Its 394 mm! Call DB Customs for exact customized length if you want. I haven't found any TB with the exact measurement, either you get a shorter one or a longer one. Got mine from AEX. They have the 384 mm one. Its one cm shorter but it works! You could also use 409mm without any barrel extensions.

guys can anybody tell me the EXACT inner barrel length of the KWA m4s tactical? Im planning to get a tightbore for my gun

You can always extend a bit into your flash hider if it is a bit longer, or you could buy on thats longer and cut it down to size. But Rockhound is correct in the lenght of the barrel. The length is stated on KWA's site (www.kwausa.com) Click there to get all the exact spec.s on your gun

hmm... I might get the 407 and just cut it. any special notes on how not to damage the inner part of the barrel when im sawing it?

Yeah, if you do it wrong, you will get jamming, ALSO REMEMBER to cut the side that is at then very end of your gun (NOT the end that goes into your hopup) If you cut the wrong end, then.... it makes a nice $50 paper weight XD

Yeah, if you do it wrong, you will get jamming, ALSO REMEMBER to cut the side that is at then very end of your gun (NOT the end that goes into your hopup) If you cut the wrong end, then.... it makes a nice $50 paper weight XD

Too long for paper weight... maybe a good "high-grade" straw for your Big-gulp.